Several interventional studies in adults have shown beneficial effects of lowering blood cholesterol levels in risk of cardiovascular disease. Before similar recommendations of diet intervention in children with elevated blood cholesterol can be made with confidence, it must first be demonstrated that this goal is feasible, acceptable, effective and safe. This RFA: Diet Intervention in Children With High LDL, proposes to systematically and thoroughly examine these aspects utilizing six collaborating clinics operating under a protocol which will closely evaluate and monitor the factors deemed important. A coordinating center will serve as a central depository of data collected for analysis. A central laboratory will provide standardized analyses. The Data and Safety Monitoring Committee (DSMC) will monitor the data and oversee the conduct of the study. The proposal will be conducted in two Phases. Phase Ia is eight-month period set aside for protocol planning. Phase 1b is a short-term (twelve-month) feasibility study to gain experience about recruitment, enrollment and implementation of the diet intervention. This experience will allow assessment of proposed procedures, intervention techniques, compliance and identification of logistical problems. Phase II is a full-scale, long- term (four-year) trial to carefully determine the feasibility, acceptability, efficacy and biological and psychological safety of diet intervention in children, ages eight to ten years, with high LDL-cholesterol. The overall objective of this important study is to allow diet recommendations for the management of children with high LDL-C which is supported by sound scientific basis. Should this proposal be funded, this investigation will be conducted in two Iowa communities, Clinton and Muscatine. These communities are demographically similar to each other as well as to the State of Iowa. The combined school populations of these two communities will provide adequate number of 8-10 year old subjects for the study. The extensive experience gained from previous studies of coronary risk factors in children and the support of the University of Iowa research resources will allow a strong multidisciplinary approach toward this important scientific endeavor.